A laser heterodyne interferometer has advanced features of high measurement speed and accuracy, high anti-interference, low sensitive to the luminous intensity variation and direct traceability to the primary standard of length, etc., therefore, is widely used in the high precision displacement measurement, ultra-precision fabrications and the detection and calibration of the instruments. Signal processing methods for laser heterodyne interferometer displacement measurement can be mainly divided into two types: phase demodulation, achieving phase measurement via measuring the phase difference between a reference signal and the measurement signals with high resolution characteristics; and frequency demodulation, achieving displacement measurement via counting the Doppler frequency directly, which has the advantage of high speed of measurement. In the frequency demodulation of heterodyne interferometric signal, during the achieving of displacement measurement via pulse counting the Doppler frequency directly, the quality of signal has direct affect on the accuracy and stability of the counting, when performing magnification to the processed heterodyne interferometric signal with oscilloscope, it is found that the rising edge of the signal is not ideal: in one aspect, the gradient of the rising edge of the signal is lower, which will lead to inaccurate trigger time of the pulse counting, thereby affecting the accuracy of phase difference detection between the reference signal and measurement signal; in another aspect, the phenomenon of multiple rising edges caused by the interference of noises and high-frequency harmonics will lead to mistaken triggering of the entire cycle interference fringe counting pulse, which will affect the accuracy of the measurement result. Therefore, improvement for the quality of the laser heterodyne interferometric signal becomes a key technical problem to be resolved when improving the accuracy and precision of measurement.